Heat strippable optical fiber ribbons

ABSTRACT

Optical fiber ribbons comprise at least two optical fibers and a matrix material in which the optical fibers are encapsulated. The matrix material exhibits a maximum tensile strength at 100° C. of at least about 1000 psi and an elongation at break at 100° C. of at least about 15%, and the ribbons are easily and cleanly heat strippable in an intact unit to allow fiber splicing.

This application claims the benefit of Provisional Application No.60/147,881, filed Aug. 9, 1999.

FIELD OF THE INVENTION

The present invention is directed to optical fiber ribbons containingradiation cured matrix materials and is directed to radiation curedmaterials suitable for use, inter alia, as matrix materials for opticalfiber ribbons. The radiation cured matrix materials have an advantageouscombination of physical properties, including good maximum tensilestrength and good elongation at high temperatures and provide theoptical fiber ribbons with improved heat strippability to allow cleanand reliable splicing of the optical fibers.

BACKGROUND OF THE INVENTION

New optical fiber technologies are continually being developed toaccommodate increasing demands for band width and other communicationproperties. Optical fiber ribbons have been developed to provideincreased packing densities, improved accessibility and the like. In theU.S. telecommunications industry, 12-fiber ribbons have become astandard while in Japan, 8-fiber ribbons have commonly been employed.Optical fiber ribbons are disclosed, for example, in the Duecker U.S.Pat. No. 5,881,194, the Lochkovic et al U.S. Pat. No. 5,561,730 and theHattori et al U.S. Pat. No. 5,524,164, and by McCreary et al,International Wire and Cable Symposium Proceedings (1998):432-439.

Generally, optical fiber ribbons comprise two or more optical fibersembedded and secured within a matrix material. The optical fibers oftencontain one primary coating, optionally with a secondary coating, oreven further additional coatings, and are typically arranged in parallelrelation substantially within a single plane to form a ribbon. Ribbonfibers provide a convenient means for splicing fibers as many fibers canbe spliced at one time. Generally, to splice the fibers, the matrixmaterial and fiber coatings must be stripped from the fibers which areto be spliced, without damaging the fibers. Thermal stripping tools areconventionally employed to heat the matrix material, for example to atemperature of about 90° C. to about 110° C., and strip it from aportion of the glass fibers. It is desirable to strip off the coatingsin an intact tube form to avoid damage to the optical fibers and/or toavoid deposit of coating debris on the fibers.

Optical fiber ribbon splicing is commonly performed in the field, and,unfortunately, the quality of the stripping operation isoperator-dependent owing to variables such as the amount of time thefiber ribbon is heated in the stripping tool and the amount of pressurewhich the operator exerts on the stripping tool. Accordingly, it isoften difficult to obtain a clean strip of the ribbon withoutdisintegration of the coatings and/or the matrix material, and someamount of coating debris typically remains on the optical fibers. Debrison the fibers can interfere with and prevent a clean splice, whileattempts to remove such debris can result in fiber breakage. Pastattempts to improve the strippability of optical fiber ribbons havefocused on primary and/or secondary coating materials typically employedon the optical fibers, as well as strip test parameters, as report byMurata, et al., International Wire and Cable Symposium Proceedings(1997): 281-288, Botelho, International Wire and Cable SymposiumProceedings (1993); 566-569, and Mills, International Wire and CableSymposium Proceedings (1992): 472-475. These studies among others in theindustry generally resulted in improvements in cleanliness upon thermalstripping. However, a need still exists in the fiber optic cableindustry for ribbons which reduce the dependence of strippability onsuch factors.

Accordingly, a need remains for providing improved optical fiber ribbonsincluding a heat strippable matrix material which allows for cleanstripping of material from the optical fibers, substantially independentof operator variability.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide opticalfiber ribbons, and particularly to provide optical fiber ribbons whichare heat strippable. It is an additional object of the present inventionto provide optical fiber ribbons which overcome disadvantages of theprior art. It is a more specific object of the invention to provideoptical fiber ribbons which allow for clean heat stripping of materialfrom the optical fibers and reliable splicing of the stripped fibers. Itis a further object of the invention to provide radiation cured matrixmaterials for use, inter alia, in optical fiber ribbons.

These and additional objects are provided by the optical fiber ribbonsand matrix materials of the present invention. More particularly, theinvention is directed to optical fiber ribbons which comprise at leasttwo optical fibers encapsulated within a radiation cured matrix materialhaving an advantageous combination of physical properties, includinggood maximum tensile strength and good elongation at high temperatures.In a more specific embodiment, the matrix materials exhibit a maximumtensile strength at 100° C. of at least about 1000 psi and an elongationat break at 100° C. of at least about 15%. The present invention is alsodirected to radiation cured matrix materials, wherein the radiationcured matrix materials exhibit a maximum tensile strength at 100° C. ofat least about 1000 psi and an elongation at break at 100° C. of atleast about 15%.

The optical fiber ribbons according to the present invention areadvantageous in that the matrix material and any underlying coatings areeasily and cleanly heat strippable from the optical fibers in an intactunit and therefore allow for reliable splicing of the stripped fibers inthe field, independent of operator variability. The matrix material alsoexhibits a good combination of mechanical and chemical properties whichare otherwise necessary for encapsulating and protecting the opticalfibers within the ribbon structure.

These and additional objects and advantages provided by the opticalfiber ribbons and matrix materials of the present invention will be morefully apparent in view of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING

The following detailed description will be more fully understood in viewof the drawing which sets forth one embodiment of the optical fiberribbons of the invention comprising four optical fibers encapsulatedwithin a radiation cured matrix material.

DETAILED DESCRIPTION

The present invention is directed to optical fiber ribbons and toradiation cured matrix materials for use, inter alia, in optical fiberribbons. The optical fiber ribbons according to the present inventioninclude at least two optical fibers encapsulated within a radiationcured matrix material. The optical fiber ribbons may comprise two,three, four, or more optical fibers as is desired for a particularapplication. While ribbons comprising four, eight and twelve opticalfibers, respectively, are commonly employed, the number of opticalfibers in a particular ribbon may be varied as desired.

Typical optical fiber ribbons in accordance with the present inventionare shown in the FIGURE which illustrates an optical fiber ribbon 10.The ribbon 10 comprises four optical fibers 16 embedded within matrixmaterial 18. As is known in the art, the ribbon may comprise subunits,wherein each subunit comprises two or more optical fibers, if desired.Typically, the optical fibers in the optical fiber ribbons of thepresent invention are arranged in parallel fashion and substantiallywithin a single plane as shown in the FIGURE. However, it is equallywithin the scope of the present invention to arrange the optical fibersin other configurations as desirable.

The structure, composition and manufacture of the individual opticalfibers 16 is well known in the art. The optical fibers may comprise, forexample, a glass core and a glass cladding layer. The core, for example,may comprise silica doped with oxides of germanium or phosphorous andthe cladding, a pure or doped silicate such as a fluorosilicate.Alternately, the fibers may comprise a polymer clad silica glass core.Examples of such polymer claddings include organosiloxanes such aspolydimethylsiloxane or a fluorinated acrylic polymer. The opticalfibers may be provided with one or more primary coatings and/orsecondary coatings in accordance with techniques known in the art toprotect the underlying glass fiber from external damaging forces and/orto improve the performance of the optical fibers. Additionally, theoptical fibers may include ink coloring as desired. In a preferredarrangement, each fiber of a ribbon or a subunit ribbon is provided witha different and distinguishing color.

In accordance with an important feature of the optical fiber ribbons ofthe present invention, the matrix material 18 has a unique combinationof advantageous properties which allow the optical fibers to be easilyand cleanly heat stripped using conventional stripping tools,substantially independent of operator variability. Specifically, thematrix material exhibits both a maximum tensile strength at 100° C. ofat least about 1000 psi and an elongation at break at 100° C. of atleast about 15%, both of which properties are measured according to ASTMD-882-95a. These properties are measured once the material has beencured at about 70° C. Generally, the maximum tensile strength representsthe peak of the stress-strain curve and often is equivalent to thetensile strength at break at higher temperatures, although for somematerials in certain temperature ranges, break does not occur at themaximum tensile strength but at a subsequent, lower tensile strength.

The combination of the recited maximum tensile strength and elongationat 100° C. provides a robust matrix material with sufficient toughnessand elongation to allow the matrix material and any underlying coatingsto be cleanly removed from the optical fibers in a single unit over awide range of temperatures, and particularly at commonly employed heatstripping temperatures of from about 90° C. to about 110° C. Matrixmaterials having the recited maximum tensile strength, typically as aresult of high glass transition temperatures, but lacking the recitedelongation, are usually brittle and therefore are not suitable for usein the present invention. Rather, the combination of both a maximumtensile strength at 100° C. of at least about 1000 psi and an elongationat break at 100° C. of at least about 15% are necessary to provide theimprovements of the invention. In preferred embodiments, the maximumtensile strength at 100° C. is at least about 2000 psi, and morepreferably is at least about 3000 psi, and the elongation at break at100° C. is at least about 30%, and more preferably is at least about40%. In further preferred embodiments, the maximum tensile strength at100° C. is at least about 2000 psi and the elongation at break at 100°C. is at least about 30%. More preferably, the maximum tensile strengthat 100° C. is at least about 3000 psi and the elongation at break at100° C. is at least about 40%.

The matrix material comprises a radiation cured composition. Preferably,the matrix material is formed by curing a radiation curable compositioncomprising (a) aliphatic urethane oligomer having acrylate ormethacrylate functionality, (b) reactive unsaturated monomer, and,optionally, (c) a photoinitiator.

The first component (a), the aliphatic urethane oligomer having acrylateor methacrylate functionality, is preferably a wholly aliphatic urethaneacrylate oligomer. Preferably, the oligomer is based on an aliphaticpolyether polyol, which is reacted with an aliphatic polyisocyanate andthen acrylated or methacrylated to provide reactive terminal groups.Silicon-containing polyether polyol backbones are suitable.Alternatively, the oligomer may be based on any combination of polyolbackbones which do not adversely affect the cured coating. Othersuitable examples of backbones include hydrocarbon polyols,polycarbonate polyols, polyisocyanate polyols, and mixtures of these.However, polyether polyol backbones are preferred, because, in general,they have good hydrolytic stability and are relatively inexpensive.Polyols which are less suitable include polyester or epoxy backbonesowing to yellowing and/or poor hydrolytic stability. The oligomericcomponent may contain very small amounts of urethane acrylates based onpolyesters, but preferably contain only the above kinds of oligomers,for optimal long term stability.

A representative polyether polyol is based on a straight chain orbranched alkylene oxide of from one to about twelve carbon atoms. Thepolyether polyol may be prepared by any method known in the art.Preferably, it has a number average molecular weight (M_(n)), asdetermined by vapor pressure osmometry, per ASTM D-3592, sufficient togive the entire oligomer a molecular weight of not more than about 6,000daltons, preferably not more than about 5,000 daltons, and morepreferably not more than about 4,000 daltons. Such polyether polyolsinclude but are not limited to polymethylene oxide, polyethylene oxide,polypropylene oxide, polybutylene oxide, and mixtures thereof.

Representative hydrocarbon polyols which may be used include, but arenot limited to, those based on a linear or branched hydrocarbon polymerhaving a molecular weight of from 600 to 4,000, such as fully orpartially hydrogenated 1,2-polybutadiene, 1,2-polybutadiene hydrogenatedto an iodine number of from 9 to 21; and fully or partially hydrogenatedpolyisobutylene. Unsaturated hydrocarbon polyols are not preferredbecause the oligomers made from them, when cured, are susceptible tooxidation. Representative polycarbonate polyols include but are notlimited to the reaction products of dialkyl carbonate with an alkylenediol, optionally copolymerized with alkylene ether diols.

The polyisocyanate component is preferably non-aromatic as oligomersbased on aromatic polyisocyanates often effect yellowing in the curedcoating. Non-aromatic polyisocyanates of from 4 to 20 carbon atoms arepreferably employed. Suitable saturated aliphatic polyisocyanatesinclude but are not limited to isophorone diisocyanate;dicyclohexylmethane-4,4′-diisocyanate; 1,4-tetramethylene diisocyanate,1,5-pentamethylene diisocyanate; 1,6-hexamethylene diisocyanate;1,7-heptamethylene diisocyanate; 1,8-octamethylene diisocyanate,1,9-nonamethylene diisocyanate, 1,10-decamethylene diisocyanate;2,2,4-trimethyl-1,5-pentamethylene diisocyanate;2,2′-dimethyl-1,5-pentamethylene diisocyanate;3-methoxy-1,6-hexamethylene diisocyanate; 3-butoxy-1,6-hexamethylenediisocyanate; omega, omega′-dipropylether diisocyanate; 1,4-cyclohexyldiisocyanate; 1,3-cyclohexyl diisocyanate; trimethylhexamethylenediisocyanate; and mixtures thereof. Very small amounts of aromaticpolyisocyanates may be used; however, long term stability on aging maysuffer somewhat.

An end capping monomer is typically employed to provide at least onereactive acrylate or methacrylate terminal group on the oligomer.Suitable hydroxyl-terminated compounds which may be used as the endcapping monomers include but are not limited to hydroxyalkyl acrylatesor methacrylates such as hydroxyethyl acrylate, hydroxyethylmethacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,hydroxybutyl acrylate, hydroxybutyl methacrylate, and so forth. Aparticularly preferred end capping monomer is hydroxyethyl acrylate orhydroxyethyl methacrylate.

Some commercially available aliphatic urethane acrylate and methacrylateoligomers which are suitable for use in this invention include, but arenot limited, to the following:

1. PHOTOMER® 6008 from Henkel Corporation, Ambler, Pa., which comprisesaliphatic urethane acrylate oligomer from polyether polyol, dicyclohexylmethane diisocyanate, and hydroxyethyl acrylate. The oligomer has anumber average molecular weight of about 1,500 daltons and is sold as asolution of the oligomer in tripropylene glycol diacrylate as diluent.

2. PHOTOMER® 6019, also from Henkel Corporation, completely analogous tothe above but based on isopherone diisocyanate rather than dicyclohexylmethane diisocyanate.

3. EBECRYL 270, from UCB Chemicals, Smyrna, Ga., which comprises analiphatic urethane diacrylate based on a polyether polyol.

4. PURELAST® aliphatic urethane acrylate oligomers based on polyetherbackbones, available from Polymer Systems Corporation, Orlando, Fla.Suitable PURELAST® oligomers include 534, 536, and 538 (trifunctionalpolyether urethane acrylates), and 544, 546 and 548 (tetrafunctionalpolyether urethane acrylates). Additional oligomers include 566, 566A,569, 569A, 586, 586A, 590, 590A, 595, 595A, 597, 597A, 598 and 598A.These oligomers increase in modulus with increasing number in the seriesand are either difunctional (no suffix) or monofunctional (“A” suffix).All of these oligomers are sold neat, except for 597A and 598A, whichinclude 7% and 10% isobornyl acrylate, respectively. Particularlypreferred from this group are PURELAST® 590 and 595. Methacrylateanalogs of these oligomers are suitable as well.

The second component (b) of the radiation curable compositions fromwhich the matrix material are formed comprises reactive unsaturatedmonomer. While the inventors do not intend to be limited by theory, itis believed that the reactive unsaturated monomer contributes to thedesired combination of maximum tensile strength and elongation. In apreferred embodiment, the reactive unsaturated monomer comprisesacrylate or methacrylate monomer or a mixture thereof, alone or incombination with other unsaturated monomers. In further preferredembodiments, the reactive unsaturated monomer comprises a mixture of atleast two reactive monomers, and more preferably comprises at least twomonomers selected from the group consisting of (i) cross-linkingmonomers, (ii) hydrogen-bonding monomers, and (iii) monofunctionalsteric-hindrance monomers. It has been discovered that combinations ofthese types of monomers can contribute to the desired combination ofhigh temperature maximum tensile strength and elongation suitable toprovide, in turn, the optical fiber ribbon having improved heatstrippability. In further preferred embodiments, the reactive monomermixture comprises a mixture of at least one of (i) the cross-linkingmonomer and (ii) the hydrogen-bonding monomer, and further comprises(iii) the monofunctional steric-hindrance monomer. Combinations ofeither the cross-linking monomer and/or the hydrogen-bonding monomerwith the monofunctional steric-hindrance monomer are particularlyadvantageous for providing the desired combination of high temperaturemaximum tensile strength and elongation.

Unsaturated cross-linking monomers are known in the art and may comprisefrom 2 to about 5, or more, functional groups. Acrylate andmethacrylate, and particularly trifunctional acrylate and methacrylatecross-linking monomers are preferred. Examples of suitable cross-linkingmonomers include, but are not limited to, trimethyloyl propanetriacrylate, alkoxylated derivatives thereof, glycerolalkoxytriacrylates, pentaerythritol-containing acrylates such aspentaerythritol tetraacrylate and dipentaerythritolmonohydroxypentacrylate, neopentyl glycol diacrylate, isocyanurate di-and triacrylate components, bisphenol-A diacrylates and dimethacrylates,alkoxylated derivatives thereof, melamine acrylate and methacrylatederivatives, polyether acrylates and methacrylates,dicylcopentyloxyethyl diacrylate, dicyclopentyloxyethyl dimethacrylate,cyclohexane dimethanol diacrylates, and the like, and mixtures thereof.In a further preferred embodiment, the cross-linking monomer comprisesan isocyanurate monomer. More preferably, the cross-linking monomercomprises a triacrylate or a trimethacrylate of an isocyanuratecompound. Trifunctional monomers, and particularly a triacrylate oftrishydroxyethyl isocyanurate, are preferred cross-linking monomers.

Unsaturated hydrogen-bonding monomers are also known in the art andgenerally include a high degree of hydrogen bonding. Examples ofhydrogen-bonding monomers include, but are not limited to, urethanemonoacrylates, including, but not limited to, those resulting fromreaction of a hydroxy alkyl acrylate and an isocyanate, for example thereaction products of hydroxypropyl acrylate and phenyl isocyanate,hydroxyethyl acrylate and butyl isocyanate, and the like. Hydrophilicmonomers such as N-vinyl formamide, N-vinyl-2-caprolactam and the likeare also suitable.

Finally, monofunctional unsaturated steric hindrance monomers are alsoknown in the art and are suitable for use in the radiation curablecompositions. Examples include, but are not limited to isobornylacrylate, isobornyl methacrylate, dicyclopentyloxyethyl acrylate,dicyclopentyloxyethyl methacrylate, tert-butyl-cyclohexyl acrylates andmethacrylates, alkoxylated derivatives thereof, and mixtures thereof.

As set forth above, it is preferred that the reactive monomer mixturecomprises a mixture of at least one of (i) the cross-linking monomer and(ii) the hydrogen-bonding monomer, and further comprises (iii) themonofunctional steric-hindrance monomer. In such embodiments, it isfurther preferred that the monofunctional steric hindrance monomercomprises at least about 20 percent by weight of the reactive monomermixture, and more preferably at least about 30 weight percent of thereactive monomer mixture, to provide the necessary elongation to thecured compositions.

An optional component of the matrix composition is a photoinitiator. Thenecessity for this component depends on the envisioned mode of cure ofthe matrix composition: if it is to be ultraviolet cured, aphotoinitiator is needed; if it is to be cured by an electron beam, thematerial may comprise no or substantially no photoinitiator. In theultraviolet cure embodiment, the photoinitiator, when used in a smallbut effective amount to promote radiation cure, must provide reasonablecure speed without causing premature gelation of the matrix composition.Further, it must not interfere with the optical clarity of the curedmatrix material. Still further, the photoinitiator must itself bethermally stable, non-yellowing, and efficient. Suitable photoinitiatorsinclude, but are not limited to, hydroxycyclohexylphenyl ketone;hydroxymethylphenylpropanone; dimethoxyphenylacetophenone;2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1;1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one;1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one;(4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone;diethoxyacetophenone; 2,2-di-sec-butoxyacetophenone; diethoxy-phenylacetophenone; bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphineoxide; 2,4,6-trimethylbenzoyldiphenylphosphine oxide,2,4,6-trimethylbenzoylethoxyphenylphosphine oxide; and mixtures ofthese. A particularly preferred photoinitiator ishydroxycyclohexylphenyl ketone, such as is supplied by Ciba SpecialtyChemicals, Tanytown, N.Y., as IRGACURE® 184.

The amounts of the respective components in the radiation curablecompositions may be varied as suitable to obtain the recited maximumtensile strength and elongation, in combination with other desiredphysical and chemical properties for the matrix material. Preferably,the radiation curable compositions comprise, by weight, from about 30%to about 80% of the urethane acrylate oligomer, from about 10% to about60% of the reactive unsaturated monomer, and from about 0.1% to about10% of the photoinitiator. More preferably, the radiation curablecompositions comprise, by weight, from about 40% to about 80% of theurethane acrylate oligomer, from about 10% to about 50% of the reactiveunsaturated monomer, and from about 1% to about 10% of thephotoinitiator. Even further preferred are radiation curablecompositions comprising, by weight, from about 40% to about 70% of theurethane acrylate oligomer, from about 30% to about 60% of the reactiveunsaturated monomer, and from about 1% to about 6% of thephotoinitiator.

The matrix material may also comprise one or more optional conventionalingredients. One optional class of components includes variousstabilizers or antioxidants. To improve shelf life (storage stability)of the uncured coating, as well as to increase thermal and oxidativestability of the cured coating, one or more stabilizers or antioxidantsmay be included in the composition. Examples of suitable stabilizersinclude organic phosphites; hindered phenols; mixtures thereof; and thelike. Some particular examples of antioxidants which can be used includepropionates such asoctadecyl-3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl)propionate andhydrocinnamates such as thiodiethylenebis(3,5-di-tert-butyl-4-hydroxy)hydrocinnamate andtetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane.When a stabilizer or antioxidant is used, it may be incorporated in anamount, for example, of from about 0.1 percent to about 2.0 percent byweight, based on the weight of the composition. Preferably, it isincluded in the range from about 0.5 percent to about 1.5 percent byweight, based on the weight of the composition. Desirable properties ofa stabilizer or antioxidant include non-migration. A preferredantioxidant is thiodiethylenebis(3,5-di-tert-butyl4′-hydroxy)hydrocinnamate, such as IRGANOX® 1035,from Ciba Specialty Chemicals, Tanytown, N.Y.

Additional optional components for use in the radiation curablecompositions include additives for reducing the coefficient of frictionof the cured compositions and/or for improving the release of the curedcompositions from the optical fibers at room temperature, i.e. improvingthe peelability of the cured compositions. Such additives are known inthe art and may include, but are not limited to, silicone materials,including silicone acrylates and silicone methacrylates, fluorocarbonsand the like.

The optical fiber ribbons are manufactured in accordance withconventional processing techniques. A plurality of inked and coatedoptical fibers are typically embedded and secured in a desiredconfiguration, e.g., in a parallel and planar or other prescribedarrangement, in the liquid radiation curable matrix composition. Theinked and coated optical fibers are disposed in a desired relationshipto each other, to form a unitary structure, which structure is producedby arranging the fibers in the desired relationship, applying the liquidmatrix composition to the fibers to embed them therein, then curing theliquid composition by exposure to curing radiation. A high focus lamp istypically employed for curing although other conventional apparatus andprocedures may be employed. The matrix composition, when cured, adheresto the ink or outer coating layer of the fibers during use and providesfor a coating structure which is easily and cleanly heat strippabletherefrom, preferably in an intact unit, without substantially damagingthe integrity of the optical fibers.

Although the radiation-cured matrix materials have been discussed hereinfor use in optical fiber ribbons, one of ordinary skill in the art willappreciate that these compositions may be useful in any embodiment whereit is desirable to coat or bind a flexible substrate. Examples of suchsubstrates include, but are not limited to, glass, metal or plastic.

The following example exemplifies specific embodiments of the matrixmaterials and optical fiber ribbons of the present invention. Throughoutthe example and the present specification, parts and percentages are byweight unless otherwise specified.

EXAMPLE

In this example, radiation curable compositions A and B are preparedcomprising about 45 parts by weight of a polyether aliphatic urethanediacrylate supplied under the commercial designation Purelast® 595,about 4 parts by weight of a photoinitiator comprising1-hydroxycyclohexyl phenyl ketone supplied under the commercialdesignation Irgacure® 184, about 1 part by weight of an antioxidantcomprising Irganox® 1035, and reactive unsaturated monomer mixtures. Incomposition A, the reactive monomer mixture comprises 25 parts by weightof triacrylate trishydroxyethyl isocyanurate supplied under thecommercial designation Sartomer SR-368 and 25 parts by weight ofisobornyl acrylate (IBOA). In composition B, the reactive monomermixture comprises 20 parts by weight of the triacrylate trishydroxyethylisocyanurate supplied under the commercial designation Sartomer SR-368,20 parts by weight of isobornyl acrylate (IBOA), and 10 parts by weightN-vinyl formamide (NVF).

The compositions are cured by exposure to ultraviolet radiation (0.7joules/cm²) at a temperature of about 70° C. using a medium pressuremercury vapor lamp and are subjected to measurement of maximum tensilestrength and elongation at 100° C. according to ASTM D-882-95a. Thecompositions and the properties (as an average of 3 measurements) areset forth in the Table.

For comparison purposes, a comparative composition C is also subjectedto similar measurements. The comparative composition C comprises about65 parts by weight of a polyether aliphatic urethane acrylate suppliedunder the commercial designation Photomer 6008, about 4 parts by weightof the photoinitiator Irgacure® 184, about 1 part by weight of theantioxidant Irganox® 1035, and reactive monomer mixture. In compositionC, the reactive monomer mixture comprises 25 parts by weight of2-phenoxyethyl acrylate (PEA) and 5 parts by weight of hexanedioldiacrylate (HDODA). The composition and the properties (as an average of3 measurements) are also set forth in the Table.

TABLE Component (parts by weight) A B C Urethane Acrylate Oligomer PE595 45 45 — Ph 6008 — — 65 Reactive Monomer SR-368 25 20 00 IBOA 25 20 —NVF — 10 — PEA — — 25 HDODA — —  5 Photoinitiator (Irgacure ® 184)  4  4 4 Antioxidant (Irganox ® 1035)  1  1  1 Property Maximum TensileStrength, 100° C., psi 1208  3113  410  Elongation, 100° C., %   31.6  53.0 13

The cured compositions A and B exhibit the desired combination ofmaximum tensile strength and elongation, while the comparativecomposition C is deficient in both of these properties.

The present examples and specific embodiments set forth in the presentspecification are provided to illustrate various embodiments of theinvention and are not intended to be limiting thereof. Additionalembodiments within the scope of the present claims will be apparent toone of ordinary skill in the art.

What is claimed is:
 1. Optical fiber ribbon, comprising at least twooptical fibers and a matrix material in which the optical fibers areencapsulated, the matrix material exhibiting a maximum tensile strengthat 100° C. of at least about 1000 psi and an elongation at break at 100°C. of at least about 15%.
 2. Optical fiber ribbon as defined by claim 1,wherein the matrix material exhibits a maximum tensile strength at 100°C. of at least about 2000 psi.
 3. Optical fiber ribbon as defined byclaim 1, wherein the matrix material exhibits a maximum tensile strengthat 100° C. of at least about 3000 psi.
 4. Optical fiber ribbon asdefined by claim 1, wherein the matrix material exhibits an elongationat break at 100° C. of at least about 30%.
 5. Optical fiber ribbon asdefined by claim 2, wherein the matrix material exhibits an elongationat break at 100° C. of at least about 30%.
 6. Optical fiber ribbon asdefined by claim 1, wherein the matrix material exhibits an elongationat break at 100° C. of at least about 40%.
 7. Optical fiber ribbon asdefined by claim 3, wherein the matrix material exhibits a n elongationat break at 100° C. of at least about 40%.
 8. Optical fiber ribbon asdefined by claim 1, wherein the matrix material and any underlyingcoatings are strippable from the optical fibers in an intact unit whenthe optical fiber ribbon is heated to about 90° C.-110° C.
 9. Opticalfiber ribbon as defined by claim 1, wherein at least four optical fibersare encased within the matrix material.
 10. Optical fiber ribbon asdefined by claim 1, wherein the matrix material is formed by curing aradiation curable composition comprising (a) aliphatic urethane oligomerhaving acrylate or methacrylate functionality, (b) reactive unsaturatedmonomer, and, optionally, (c) a photoinitiator.
 11. Optical fiber ribbonas defined by claim 10, wherein the reactive unsaturated monomer (b)comprises a mixture of at least two reactive unsaturated monomers. 12.Optical fiber ribbon as defined by claim 11, wherein the reactiveunsaturated monomer mixture comprises at least one acrylate ormethacrylate monomer.
 13. Optical fiber ribbon as defined by claim 12,wherein the reactive unsaturated monomer mixture comprises at least twomonomers selected from the group consisting of (i) cross-linkingmonomers, (ii) hydrogen-bonding monomers, and (iii) monofunctionalsteric-hindrance monomers.
 14. An optical fiber matrix as defined byclaim 13, wherein the cross-linking monomer comprises a triacrylate ortrimethacrylate.
 15. An optical fiber ribbon as defined by claim 10,wherein the radiation curable composition comprises, by weight, fromabout 30% to about 80% of the urethane acrylate oligomer, from about 10%to about 60% of the reactive unsaturated monomer, and from about 0.1% toabout 10% of the photoinitiator.
 16. An optical fiber ribbon as definedby claim 10, wherein the radiation curable composition comprises, byweight, from about 40% to about 80% of the urethane acrylate oligomer,from about 10% to about 50% of the reactive unsaturated monomer, andfrom about 1% to about 10% of the photoinitiator.
 17. An optical fiberribbon as defined by claim 10, wherein the radiation curable compositioncomprises, by weight, from about 40% to about 70% of the urethaneacrylate oligomer, from about 30% to about 60% of the reactiveunsaturated monomer, and from about 1% to about 6% of thephotoinitiator.
 18. An optical fiber ribbon as defined by claim 13,wherein the reactive unsaturated monomer mixture comprises a mixture ofat least one of (i) cross-linking monomer and (ii) hydrogen-bondingmonomer, and further comprises (iii) monofunctional steric-hindrancemonomer.
 19. A radiation cured material having a maximum tensilestrength at 100° C. of at least about 1000 psi and an elongation atbreak at 100° C. of at least about 15% and formed from a radiationcurable composition comprising (a) aliphatic urethane oligomer havingacrylate or methacrylate functionality, (b) reactive unsaturated